Eventually a suitable programmable unit (“the brains”) was acquired, an old industrial computer, known as a Programmable Logic Controller (“PLC” for short), now made redundant after about 15 years of 24/7 active service, but still in good working order. Yes, even working computers get made redundant these days!

This PLC would be able to hold all the “actions” in a sequential program and switch relays on and off as required.

Relays were necessary to switch the light elements on and off as the PLC outputs had only a low voltage capability (24v) and could not switch “Mains” equipment directly . These “interposing relays” were to be used between the PLC outputs and the 230V AC rope lighting elements to do the on/off switching as directed by the PLC’s program.

Once all the other parts (relays, bases, protective units, power supplies, cable etc., and also a large weatherproof box to put it all in) were ordered and received, “the build” could begin.